This application is based on Japanese Patent Application Ser. No. 115829/2001, filed Apr. 13, 2001, which is incorporated herein by reference for all purposes and from which priority is claimed.
1. Technical Field of the Invention
The present invention relates to a fuel-injection device of electromagnetic driving type, for injecting fuel into an air-intake system of an internal combustion engine at predetermined times, and more particularly, to a fuel injection device adapted to be integrated, as fuel injection means, into an air-fuel mixture generating device equipped with a diaphragm-type fuel pump and designed to be employed in place of an ordinary carburetor.
2. Description of the Related Art
An air-intake system of a small air-cooled two-stroke gasoline engine of crankcase-precompression type (hereinafter, referred to simply as an internal combustion engine), designed to be mounted on a portable working machine such as a chain saw or a brush cutter, frequently employs, as an air-fuel mixture generating device, a floatless diaphragm-type carburetor. The carburetor is ordinarily equipped with a diaphragm-type fuel pump, which is designed to receive fuel and subsequently inject pressurized fuel in conformity with pressure changes (pulsating pressure) inside a crankcase of the internal combustion engine in order to ensure a stable fuel supply to the engine irrespective of the engine posture.
However, it is often difficult to precisely control the air/fuel ratio, i.e., a quantity of fuel relative to a quantity of the intake air, using a diaphragm-type carburetor, and to achieve sufficient fuel atomization and faithful response to the pulsating pressure, thereby making it difficult to effectively take measures for purifying the exhaust gas.
With a view to addressing these problems, an air-fuel mixture generating device, equipped with a fuel injection valve in addition to a diaphragm type fuel pump, has been recently proposed as an alternative to the aforementioned carburetor.
This air-fuel mixture generating device includes a main body similar to the carburetor, and a diaphragm disposed inside the main body. A pulsating pressure chamber, to which the pressure of the crankcase is transmitted, is provided on one side of the diaphragm, and a pump chamber for receiving fuel and then injecting fuel to a fuel passageway is provided on the other side of the diaphragm. The diaphragm is actuated (reciprocating movement) by the pressure changes (pulsating pressure) in the crankcase, resulting from the piston movement, i.e., a decrease in pressure as the piston is moved upward and an increase in pressure as the piston is moved downward. The pressurized fuel is thereby enabled to be fed from the pump chamber to the fuel passageway, and also the fuel inside the fuel passageway is enabled to be pressurized. Simultaneously, the aforementioned fuel injection valve is allowed to open at predetermined times (for example, at the moment of initiating the suction stroke) and remain open for a predetermined time period (for example, 1 to 3 milliseconds), depending on the operative conditions of the internal combustion engine to thereby enable the pressurized fuel in the fuel passageway to be injected into the intake system (for example, an intake passage portion located on a downstream side of a throttle valve) and be mixed with the received air, thereby producing an air-fuel mixture.
However, in such an air-fuel mixture-generating device, insufficient atomization of the fuel that has been injected from the fuel injection valve allows for a substantial portion of the injected fuel to adhere onto a sidewall of the intake passageway without being mixed with the air flowing through the passageway.
Additionally, if fuel atomization is insufficient, the air-fuel mixture becomes non-uniform, thereby badly affecting its combustibility in the internal combustion engine and, thus, the engine performance may deteriorate.
Moreover, even various modifications that have been suggested, such as increasing the supply pressure of fuel (fuel pressure) fed to the fuel injection valve, or decreasing a pore diameter of an injection port of the fuel injection valve, fail to achieve sufficient fuel atomization, and, thus, fail to overcome the aforementioned problems.
For example, in case where the pressurized fuel is fed to the fuel injection valve via a diaphragm-type fuel pump driven by the pressure changes (pulsating pressure) inside a crankcase of an internal combustion engine (e.g., when the aforementioned air-fuel mixture-generating device is employed), a delivery pressure effected by the diaphragm-type fuel pump is relatively low. Thus, when a pore diameter of an injection port of the fuel injection valve is decreased, the injection port is more likely to be clogged with dust, thereby obstructing the feeding of fuel. Accordingly, there exists a need in the art for a fuel injection device capable of enhancing fuel atomization and for an air-fuel mixture generating device equipped with such a fuel injection device, which can overcome the aforementioned disadvantages associated with the prior fuel-injection and air-fuel mixture-generating devices.
An object of the present invention is to provide a fuel injection device which is capable of effectively enhancing fuel atomization as the fuel is injected from a fuel injection valve without increasing the fuel supply pressure fed to the fuel injection valve, or decreasing a pore diameter of an injection port of the fuel injection valve.
Another object of the present invention is to provide an air-fuel mixture generating device equipped with such a fuel injection device.
These and other objects of the present invention, which will become apparent with reference to the disclosure herein, are attained by the provision of a fuel injection device which includes an electromagnetic driving-type fuel injection valve for injecting fuel into an air-intake passageway of an intake system of an internal combustion engine at predetermined times, the fuel injection valve being provided with a collision plate adapted to be disposed in the air-intake passageway for enabling the injected fuel to collide therewith.
Preferably, the collision plate includes a reflecting surface, disposed downstream of the fuel injection valve, inclined so as to enable the fuel that has collided against the reflecting surface to reflect therefrom and diffuse along the direction of air flow running through the air-intake passageway of the intake system.
The reflecting surface may also be provided with restricting means such as a U-shaped groove for restricting the direction of reflection and diffusion of the fuel that collides with the reflecting surface, directed in line with the direction of the air flowing through the air-intake passageway, as well as in line with a direction intersecting orthogonally with a fuel-injecting direction of the fuel injection valve.
In another embodiment, an air-fuel mixture generating device according to the present invention comprises a main body, a diaphragm-type fuel pump disposed in the main body, a fuel passageway in the main body operationally coupled to the fuel pump for receiving and pressurizing the fuel injected from the fuel pump in conformity with pressure changes inside a crankcase of an internal combustion engine, a fuel injection device mounted on the main body and operationally coupled to the fuel passageway for receiving the pressurized fuel therefrom and injecting the pressurized fuel into an air-intake passageway of an air-intake system of the internal combustion engine, and the fuel injection device comprising a collision plate for colliding with the injected fuel.
According to the air-fuel mixture generating device of the present invention as constructed above, the fuel that is injected from the fuel injection device is forced to flow rod-like and to collide with a reflecting surface of the collision plate disposed in the air-intake passageway of the intake system, thereby enabling the fuel to be atomized and scattered as it is reflected from the reflecting surface. As a result, the atomization of fuel is promoted, so that most of the fuel injected from the fuel injection valve is permitted to diffuse into and be mixed with the air flowing through the air-intake passageway without being adhered onto the sidewall of the air-intake passageway. Therefore, it is now possible to uniformly mix the fuel and air, thereby enabling the combustibility of the air-fuel mixture to be enhanced in the internal combustion engine and hence improve the engine performance.
In yet another embodiment of the present invention, an air-cooled two-stroke gasoline engine of the crankcase precompression type having an air-intake passageway with a throttle valve having a downstream side disposed in the air-intake passageway, the air-intake passageway including a throat portion provided in a main body of an air-fuel mixture-generating device downstream of the throttle valve, wherein the improvement includes a fuel injection valve having a collision plate and a fuel injection port, the fuel injection valve being arranged at the throat portion provided on the downstream side of the throttle valve, the injecting direction of fuel from the injection port being orthogonal to a direction of the air flowing through the air-intake passageway.
As previously described, according to the fuel injection device of the present invention, since it is possible to effectively enhance the atomization of fuel being injected by the fuel injection valve without increasing the fuel supply pressure, or decreasing the pore diameter of the injection port of the fuel injection valve, the fuel injection device of the present invention is quite suited for being integrated, as fuel injection means, into an air-fuel mixture generating device wherein fuel is designed to be fed, under an enhanced pressure, to the fuel injection valve by means of a diaphragm-type fuel pump which is designed to be driven via the pressure changes (pulsating pressure) inside the crankcase of the internal combustion engine.
In accordance with the invention, the objects as described above have been met and the need in the art for a fuel-injection device and an air-fuel mixture generating device capable of effectively enhancing fuel atomization as the fuel is injected without increasing the fuel supply pressure or decreasing a pore diameter of an injection port of the fuel injection device, has been satisfied.